Control bracelet

A control bracelet was a device worn upon the wrist of Eymorg inhabitants of Sigma Draconis VI. It had several functions such as the ability to control the operation of a pain band and to render an individual unconscious. It was so powerful that it could render the entire crew of a ship unconscious. The Eymorg leader Kara used this device to render the entire crew of the USS Enterprise unconscious when she sought to steal CommanderSpock's brain. (TOS: "Spock's Brain")